Method and apparatus for providing high speed recording on an optical medium

ABSTRACT

A system and method for controlling the position of an optical head of a disc during high speed recording. In one embodiment of the method, an optical disc has a plurality of tracks. The method comprises implementing CLV recording by said optical drive, determining a wobble signal based on address information contained in said plurality of tracks of said optical disk and determining a wobble clock signal based on said wobble signal. The method further comprises decoding said wobble clock signal by a decoder, said decoder to provide a sync clock signal to an encoder loop circuit, said sync clock signal based on said wobble clock signal generating an encoder clock signal using said encoder loop circuit. In addition, the method comprises comparing said sync clock signal to said encoder clock signal to provide a position command to position the optical head of said optical drive.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates in general to optical disk storagesystems and more particularly, to a method and apparatus for providinghigh speed optical disk recording.

[0003] 2. Description of the Related Art

[0004] In recent years, optical disk devices have been used to record orreproduce large amounts of data. Optical disks are storage mediums fromwhich data is read and to which data is written by laser. Each opticaldisk can store a large amount of data, typically in the order of 600-700Mbytes. Such optical disk devices are under active technicaldevelopments for achieving higher recording density.

[0005] There are generally two methods of controlling the rotating speedof an optical speed. The first is constant linear velocity (CLV)recording, in which constant linear velocity is provided duringrecording by varying the speed of the spindle motor when recordingproceeds from the inner to the outer diameter of the disk. The second isconstant angular velocity (CAV) recording, in which constant angularvelocity is provided during recording, while changing the frequency ofdata recording when recording proceeds from the inner to the outerdiameter of the disk.

[0006] Current writable optical disks include spiral-shaped grooves inthe dye coated layer (on the disk) that is sensitive to laser beams. Thegroove is not a perfect spiral, but wobbled in order to obtain motorcontrol and timing information. Recording is implemented in the grooveby locally heating up the sensitive layer with a laser spot. The laseroutput is modulated with the information to be recorded. The parts ofthe disc that were heated up during recording show a reflection decreaseafter recording and are called pits. The encoded Audio or Datainformation is stored in the length of these pits and in the distancesbetween them. These lengths and distances only take discrete values.

[0007] The data synchronization and address information for the disk isprovided through a signal typically referred to as a wobble signal. Thewobble signal is typically a frequency modulated signal with bi-phasecoded address information called Absolute Time in Pre-Groove (ATIP).

[0008] In CLV recording, the motor speed at the inner diameter istypically high, and gradually decreases as the optical head moves towardthe outer diameter. In CAV recording, the spindle motor operates at aconstant speed, but the data recording frequency varies as the opticalhead moves from the inner diameter to the outer diameter of the disk.The recording speed in optical disk recording is typically limited dueto two factors. The first arises due to mechanical limitations inproviding maximum rotational speed at the inner diameter. The secondarises due to limitations in electronic data recording rate at the outerdiameter.

[0009] To increase the speed of writing on optical disks, some drivesutilize a Zoned CLV recording in which the disc is divided into a fewzones. In a given zone, the CLV speed, or the data rate is constantwhile rotational speed decreases. At the beginning of each zone, therotational speed is the same and thus the method utilizes the maximummechanical speed limitation. However, as the CLV recording speed, or thedata rate increases, it becomes increasingly difficult for the servoloop to keep the recorded data in synchronism with the ATIP due toelectromechanical limitations. In addition, the Zoned CLV recordingrequires stopping the recording at the zone boundary and going back tore-link the recorded segment of the previous zone. Similarly, as the CAVrecording speed increases, it also becomes increasingly difficult forthe electronic circuits to keep up the data rate and may reach the datarate limitation. In this situation, a seamless writing transition fromCAV method to CLV method becomes very desirable. This is called aPartial CAV recording method.

[0010] Currently, in partial CAV recording, a technique known as pseudoCLV motor speed control is typically utilized. In this technique, themotor speed control is provided while in CAV mode. The motor speedreference is gradually changed in steps according to a prescribed way toemulate CLV. In using such a technique, the ATIP address needs to beconstantly monitored and the reference speed must be constantly changed,requiring additional servo overhead.

[0011] Accordingly, there is a need in the technology to overcome theaforementioned problems. There is also a need in the technology toobtain maximum recording speed efficiency without interruption duringwriting on a disc.

BRIEF SUMMARY OF THE INVENTION

[0012] A system and method for controlling the position of an opticalhead of a disc during high speed recording. In one embodiment of themethod, an optical disc has a plurality of tracks. The method comprisesimplementing CLV recording by said optical drive, determining a wobblesignal based on address information contained in said plurality oftracks of said optical disk and determining a wobble clock signal basedon said wobble signal. The method further comprises decoding said wobbleclock signal by a decoder, said decoder to provide a sync clock signalto an encoder loop circuit, said sync clock signal based on said wobbleclock signal generating an encoder clock signal using said encoder loopcircuit. In addition, the method comprises comparing said sync clocksignal to said encoder clock signal to provide a position command toposition the optical head of said optical drive.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013]FIG. 1 illustrates one embodiment of an optical disk apparatusprovided in accordance with the principles of the invention.

[0014]FIG. 2 illustrates one embodiment of the tracking CLV servocircuit 118 of FIG. 1.

[0015]FIG. 3 illustrates one embodiment of the Encoder Phase Lock Loopof FIG. 1.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0016] One aspect of the invention relates to an apparatus and methodfor providing high speed recording on an optical medium. In oneembodiment, a tracking CLV mode motor control technique is used duringrecording.

[0017] Referring now specifically to the figures, FIG. 1 illustrates oneembodiment of an optical disk apparatus 100. The optical disk apparatus100 includes an optical disk 102 that is rotated by a spindle motor 104.An optical pickup 106 scans the tracks on the rotating optical disk 102with a laser beam 110 a. The optical pickup 106 comprises an opticalsystem, including a laser 108 that provides a light source and anobjective lens 110. The laser 108 is driven by a laser driver 120 toemit the laser beam 110 a. The laser beam 110 a is incident on theobjective lens 110 via optical elements (not shown) such as a collimatorlens and a beam splitter. The laser beam 110 a is focused on therecording surface of the optical disk 102 by the objective lens 110 toform a small spot on the recording surface.

[0018] The light reflected from the optical disk 102 propagates back tothe objective lens 110 and is separated from the incident laser beam bythe beam splitter (not shown). The reflected light beam may then bedetected by the photodetector 122, which is able to convert thereflected light beam into electric signals. The electric signals maythen provided to a preamplifier 124, which amplifies and conditions theelectric signals. Based on the received electric signals, thepreamplifier 124 generates a plurality of signals, including a Wobblesignal (W). The Wobble signal (W) is a timing marker that also providesaddress information. In one embodiment, the Wobble signal (W) is afrequency modulated Frequency Shift Key signal with bi-phase codedaddress information called ATIP. It is understood that additionalsignals may be provided by the preamplifier 124.

[0019] The spindle motor 104 is rotated by motor driver 114. The motordriver 114 may be controlled by a CAV Servo circuit 116 or a trackingCLV Servo circuit 118. In one embodiment, the motor driver 114 has aterminal S0 and is coupled to switch S via terminal S0. The switch Sfurther comprises two terminals S1 and S2. The terminals S1 and S2 arecoupled to the CAV Servo circuit 116 and tracking CLV Servo circuit 118,respectively. The switch S may, under the direction of system controller130, operate in a CAV Mode, which connects S0 to S1, or in a TrackingCLV Mode, which connects S0 to S2. In one embodiment, switch S isdirected by the system controller 130 to connect the motor driver 114 tothe CAV Servo circuit 116, by connecting S0 to S1, when the opticalpickup 106 is in a seek mode. When the optical pickup 106 is positionedand ready for a write operation and a CLV recording process is selected,system controller 130 may direct switch S to couple S0 to S2, therebyconnecting the motor driver 114 to the tracking CLV Servo circuit 118.Alternatively, if a CAV recording process is selected, the motor driver114 may be coupled to the CAV Servo circuit 116.

[0020] In one embodiment, clock synthesizer 140 generates theappropriate clock signals (C1 and C2) for the CAV Servo circuit 116 andthe CLV Servo circuit 118 via signal lines 142 and 144, respectively.These clock signals, C1 and C2 become the reference clocks for the CAVand CLV servo loops, respectively. The clock synthesizer 140 may alsogenerate clock signal C3 for the Encoder Phase Lock Loop (Encoder PLL)150, as provided via the multiplexor (MUX) 152. The system controller130, which is coupled to the clock synthesizer 140, controls the timingof clock signals C1, C2 and C3. For example, the system controller 130may generate C1 and C2 based on the programmed CAV and tracking CLVservo circuit 116 and 118 requirements.

[0021] When the optical pickup 106 is in motion (i.e., during the seekmode), there is no Wobble signal (W) for the Encoder PLL 150 to lockonto. However, the system controller 130 has information on the targettrack and the target Wobble frequency. As a result, the clock signal C3,provided to the Encoder PLL 150 via signal line 148, is selected by thesystem controller 130 for the Encoder PLL 150 to lock onto while theoptical pickup 106 is in motion. When the optical pickup 106 is ontrack, the system controller 130 directs the MUX 152 to latch clocksignals from ATIP Decoder 160.

[0022] When the optical pickup 106 is positioned for recording (i.e.,during tracking mode), the Wobble signal (W) is provided by thepreamplifer 124 to the CLV Servo circuit 118 via signal line 126. TheWobble signal (W) is further processed by the CLV Servo circuit 118 toprovide a Wobble clock signal (Wo), which may then be used as the feedback signal 128 for the CLV servo loop. In one embodiment, Wo is decodedby an ATIP decoder 160 to provide ATIP Sync Clock signals via signalline 132, ATIP Sync signal via signal line 134 and ATIP data signals viasignal line 136. The ATIP sync clock signals are latched into the MUX152 under the control of system controller 130, and provided to theEncoder PLL 150. The Encoder PLL 150 generates an Encoder clock signalC_(E) and a target Wobble center frequency signal CF. The Encoder clocksignal C_(E) is provided to a Write Strategy Encoder Block 170 viasignal line 154, which also receives the ATIP sync signal from the ATIPdecoder 160 via signal line 134. Based on these two signals, the EncoderBlock 170 may then generate an output signal to direct the laser driver120 to position the optical pickup 106. In addition, the target Wobblecenter frequency signal CF may be provided to the preamplifier 124 viasignal line 137.

[0023] As will be described in more detail below, the Encoder PLL 150,while recording in either a CAV and Tracking CLV mode, may provide thebasic write clock signal that is locked to the ATIP Sync clock derivedby the ATIP Decoder 160 from the Wobble signal that is extracted fromthe disk. The ATIP decoder 160 may further include an ATIP Clock PhaseLock Loop to extract the ATIP Sync clock. In one embodiment, the ATIPPhase Lock Loop has a low pass filter to block the ATIP data and to passthe higher frequency component (such as the ATIP Sync clock). When theWobble signal encounters defects (after the ATIP Sync clock has beenfiltered), the ATIP Sync clock tends to free run, and supplies acontinuing ATIP Sync clock for a period corresponding to the low passfilter. For instance, at the lowest CLV speed, the wobble clock is 22.05KHz and ATIP Sync clock is 6.3 KHz, maintaining a 3.5 to 1 ratio. Thelow pass filter is generally set below 4 KHz. At higher speeds, theseparameters each increase proportionally. If a defect in the disk causesup to four or five wobble signals, ATIP Clock phase lock loop will loseinput to the phase lock loop. However, the output of the phase lock loopwill change at a rate controlled by the low pass filter and the ATIPSync clock will supply the Sync clock for a time corresponding to thefilter bandwidth. In addition, while performing either a partial or afull CLV recording operation, the same method used in the CAV mode forgenerating the Encoder Sync clock may also be used in a Tracking CLVmode.

[0024] Another aspect of the present invention is to use a Tracking CLVmode to control motor speed. As will be described in more detail below,the Wobble signal from the disk may be used to control the disk motorspeed while in a Tracking CLV mode. To improve the speed accuracy,Automatic Phase Control loop 210 (APC) is added to the Automaticfrequency Control (AFC) loop 220. When operating under the tracking CLVmode motor speed control, the Encoder PLL 150 is locked to the ATIP Syncclock and generates an Encoder clock signal for the recording process.Thus, in one embodiment, the Encoder PLL 150 may track the mechanicalclock geometry on the individual disk and write data to the disksynchronously.

[0025]FIG. 2 illustrates one embodiment of a detailed block diagram ofthe Tracking CLV Servo Circuit 118 of FIG. 1. The Tracking CLV ServoCircuit 118 receives inputs from the Clock Synthesizer 140 and thePreamplifier 124. In particular, the Tracking CLV Servo Circuit 118receives clock signal C2 via signal line 144 from the Clock Synthesizer140 and the Wobble signal (W) via signal line 126 from preamplifier 124.In one embodiment, the clock signal C2 operates at three times the rateof the Wobble Signal (W). The Wobble Signal (W) is first digitized by adigitizer 200 and then divided by divider 202 to provide W′. In oneembodiment, W is divided by 3 so that W will match the clock rate C2. Itis understood that W may be divided by any positive nonzero integer, asdetermined by the designer. The resulting signal W′ is received bycomparator 204, which also receives clock signal C2 as one input. Thecomparator 204 compares the signals C2 and W′ and provides the resultingsignal to two loops. In particular, comparator 204 provides C2 and W′ tothe Automatic Phase Control circuit (APC) 210 and an Automatic FrequencyControl circuit (AFC) 220. The APC circuit 210 comprises a divider 212and a Gain circuit 214, while the AFC circuit 220 comprises a gaincircuit 222. In one embodiment, Wp is the gain of the APC circuit 210while Wv is the gain for the AFC circuit 220. In one embodiment, Wp isbetween 6.28 and 188.4, while Wv is between 2 and 3. The divider 212divides the incoming signal to provide a wider phase range comparison.For example, in one embodiment divider 212 uses a denominator of between12 and 24 in dividing the incoming signal. The outputs of the APCcircuit 210 and circuit 220 are added by summer 230 and provided to amodulator 240. In one embodiment, the modulator is a pulse-widthmodulator. The modulator modulates the summed signals and generates anoutput that is provided to the motor driver 114 via switch S.

[0026] One aspect of the invention involves the use of an Encoder PLL150 to lock the Encoder clock to the Wobble signal W through the ATIPSync clock. In one embodiment, the ATIP decoder 160 provides the EncoderPLL 150 with an ATIP Sync clock signal (AC) via signal line 132 as adynamic reference clock. The Encoder PLL 150 multiplies clock signal(AC) by a number (Nc) to generate the Encoder clock signal (C_(E)). Inone embodiment, Nc is 343. The Encoder PLL 150 can also be locked to theWobble clock. In the latter case, clock signal (AC) has to be multipliedby 196 to generate the same Encoder Clock signal (C_(E)).

[0027]FIG. 3 illustrates one embodiment of a detailed block diagram ofthe Encoder PLL 150 of FIG. 1. The Encoder PLL 150 receives the ATIPclock signal (AC) via signal line 138, and generates the encoder clocksignal C_(E) as an output, where clock signal C_(E) tracks the Wobblesignal (W) on the disk. The Encoder PLL 150 comprises a filter 300, adividing circuit 310, a comparator 320, a phase detector 330 and avariable clock oscillator (VCO) 340. In one embodiment, the filter 300comprises capacitors CC1 and CC2, which are arranged in parallel, andresistor R which is coupled in series with capacitor CC2. In a furtherembodiment, the filter defines a type II PLL which has double poles atthe origin, as is understood by one of skill in the art. The phasedetector 330 has a gain (Kp) while the VCO 340 provides a gain (Kv). Inone embodiment, Kp=(2/6.28) μA per radian, Kv=(80×6.28) M radian/volt,CC1 is 0.0027 μF, CC2 is 0.047 μF and R is 4.3 Kohms.

[0028] When operating in the Tracking CLV mode, the Encoder PLL 150 hasto track the spindle motor speed and provide true Constant LinearVelocity recording regardless of any instantaneous speed variation inthe disk motor. The disk motor disturbance frequency is typically under200 Hz and thus the Encoder PLL 150 will electronically track themechanical inaccuracies in the disk motion. Accordingly, at the start ofthe write mode during Tracking CLV Mode, a reference Encode Sub-codeFrame Sync (ESFS) signal is phased locked with the ATIP sync clocksignal. Thereafter, the ATIP Sync clock signal may only be monitored forirregularities of the disk, such as large disk defects. If a largedefect occurs, the writing stops and the system skips over the defect.The recording reinitiates at the start of the next ATIP SYNC mark.

[0029] The present recording technique may also be implemented in a CAVrecording process. This may be initiated by directing the switch S toconnect S0 to S1, such that the system operates in the CAV servo mode,where the disk motor operates at a constant speed, while the frequencyof the data recording varies. In this mode, the Encoder PLL 150 willtrack the ATIP sync clock, which will constantly vary as the opticalhead 106 moves from the inner to the outer diameter of the disk. Thepower of the recording write laser beam 110 a depends on the writingspeed N, where N is typically an integer. In a CAV recording process,the power required during the write process changes with the address inATIP. The multi-speed media compliant disk has a linear write powerrequirement based on N. In one embodiment, the lowest speed occurs atN=1. A typically value of N is 48. If the CAV speed at the innerdiameter is N1 and the final CAV position is N2, then the write powerhas to be changed linearly for the power value corresponding to N1 tothe power value corresponding the N2. The power change may be updated atintervals of every 30 s or less. The following expression may be used tocompute the required power level at a corresponding ATIP location:$N_{x} = {{KRPM}*\sqrt{\frac{{ATIPSS} + {K2}}{K1}}}$

[0030] where,

[0031] N=the speed factor at the ATIP location;

[0032] ATIPSS=the ATIP in sum of seconds;

[0033] KRPM=thousands of revolutions per minute;

[0034] K1=179.14 multiplied by the stamped wobble speed as measured wheninitiating to write to the disk (m/s); and,

[0035] K2=1226.5625 divided by the stamped wobble speed (m/s).

[0036] If the drive components in the system are such that there is noelectronic recording data rate limitation, then the drive can performfull CAV write on an entire disc. If the drive has a recording data ratelimitation, then the drive may proceed with a CV recording until itreaches a point where a predetermined data rate limitation point hasbeen reached by monitoring the ATIP address. When it reaches this point,the drive may continue writing at a tracking CLV mode withoutinterruption in writing, maintaining a seamless write process. This typeof recording is called a partial CAV recording.

[0037] One aspect of the present invention is to use a mixed mode ofrecording, such as a partial CAV recording mode. In one embodiment, aCAV recording process is implemented until the optical head detects anATIP location where the data rate limit is reached, and CLV recording isdesired. At this point, the switch S is coupled to terminal S2, so thatthe motor driver 114 is coupled to the Tracking CLV servo circuit 118.The encoder clock source is unchanged from the CAV recording mode, whichtracks the mechanical motion of the disk. The mechanical disturbanceswhich may occur while changing servo modes from CAV to Tracking CLV doesnot affect the timing accuracy of the encoder clock as the Encoder PLLbandwidth far exceeds the slow mechanical motion disturbances. As aresult, recording is uninterrupted throughout the entire disk recordingprocess while maximizing the time efficiency in recording.

[0038] While certain exemplary embodiments have been described and shownin the accompanying drawings, it is to be understood that suchembodiments are merely illustrative of and not restrictive on the broadinvention, and that this invention not be limited to the specificconstructions and arrangements shown and described, since various othermodifications may occur to those ordinarily skilled in the art.

What is claimed:
 1. A method for positioning an optical head of anoptical disc, said optical disc having a plurality of tracks, the methodcomprising: operating in a constant linear velocity (CLV) recordingmode; determining a wobble signal based on address information containedin said plurality of tracks of said optical disc; determining a wobbleclock signal based on said wobble signal; decoding said wobble clocksignal by a decoder, to provide a sync clock signal to an encoder loopcircuit, said sync clock signal based on said wobble clock signal;generating an encoder clock signal by said encoder loop circuit; and,comparing said sync clock signal to said encoder clock signal to providea output signal to position the optical head of said optical drive. 2.The method of claim 1 wherein said wobble signal is a frequencymodulated Frequency Shift Key (FSK) signal with bi-phase coded addressinformation.
 3. The method of claim 2 wherein determining a wobble clocksignal based on said wobble signal comprises determining, by a CLV servocircuit, a wobble clock signal based on said wobble signal, said CLVservo circuit to drive a spindle motor of said optical drive to maintainsaid constant linear velocity.
 4. The method of claim 1 whereingenerating an encoder clock signal comprises receiving the sync clocksignal from said decoder by said encoder loop circuit, multiplying saidsync clock signal by a predetermined number to generate the encoderclock signal.
 5. The method of claim 1 wherein said decoder is anAbsolute Time in Pre-Groove (ATIP) decoder and said sync clock signal isan ATIP sync clock signal.
 6. The method of claim 1 wherein said encoderloop circuit is a type II Encoder Phase Lock Loop circuit.
 7. The methodof claim 1 further comprising receiving, during a seek mode, a referenceclock signal by said encoder loop circuit, said encoder loop circuit tolock onto said reference clock signal during said seek mode instead ofsaid sync clock signal.
 8. The method of claim 1 wherein entering theCLV recording mode comprises entering the CLV recording mode, phaselocking the sync clock signal with a reference clock signal uponentering said CLV recording mode.
 9. The method of claim 8, wherein saidsync clock signal is compared with said reference clock signal only uponan occurrence of an irregularity.
 10. The method of claim 1 furthercomprising: entering a continuous angular velocity (CAV) recording mode;varying the sync clock signal as the optical head of the optical drivemoves from an inner diameter to an outer diameter of said optical disk;and, tracking said sync clock signal with the encoder loop circuit. 11.The method of claim 10 wherein a write power of the optical head dependson a write speed of said optical drive, said write power to varylinearly between a first point at the inner diameter and a destinationpoint.
 12. The method of claim 1 further comprising: providing a partialCAV recording mode, said partial recording mode comprising: performing aCAV recording operation under a recording rate limit is reached,switching a motor drive of the optical drive from a CAV servo to a CLVservo; and, maintaining said encoder clock signal during said switching.13. A system for positioning an optical head during a recordingoperation comprising: an optical disc containing data, said optical headto perform the recording operation on said optical disc and to produce awobble signal based on address information contained on said opticaldisc; a controller circuit to cause said system to operate in a constantlinear velocity (CLV) recording mode; a tracking CLV circuit to receivethe wobble signal from the optical head and to determine a wobble clocksignal based on said wobble signal; a decoder, coupled to the trackingCLV circuit, to receive said wobble clock signal and to generate a syncclock signal, said sync clock signal based on said wobble clock signal;an encoder loop circuit, coupled to the decoder, to receive said syncclock signal and to generate an encoder clock signal; and, an encoderblock, coupled to the encoder loop circuit and the decoder, said encoderblock to receive and compare said sync clock signal to said encoderclock signal and, based on said comparing, provide a position command toposition the optical head during said recording operation.
 14. Thesystem of claim 13 wherein said wobble signal is a frequency modulatedFrequency Shift Key (FSK) signal with bi-phase coded addressinformation.
 15. The system of claim 14 wherein determining a wobbleclock signal based on said wobble signal comprises determining a wobbleclock signal based on said wobble signal using a CLV servo circuit, saidCLV servo circuit to drive a spindle motor of said optical drive tomaintain said constant linear velocity.
 16. The method of claim 13wherein generating an encoder clock signal comprises receiving the syncclock signal from said decoder by said encoder loop circuit, multiplyingsaid sync clock signal by a predetermined number to generate the encoderclock signal.
 17. The method of claim 13 wherein said decoder is anAbsolute Time in Pre-Groove (ATIP) decoder and said sync clock signal isan ATIP sync clock signal.
 18. The method of claim 13 wherein saidencoder loop circuit is a type II Encoder Phase Lock Loop circuit. 19.The method of claim 13 further comprising receiving, during a seek mode,a reference clock signal by said encoder loop circuit, said encoder loopcircuit to lock onto said reference clock signal during said seek modeinstead of said sync clock signal.
 20. The method of claim 13 whereinentering the CLV recording mode comprises entering the CLV recordingmode, phase locking the sync clock signal with a reference clock signalupon entering said CLV recording mode.
 21. The method of claim 13,wherein said sync clock signal is compared with said reference clocksignal only upon an occurrence of an irregularity.
 22. The method ofclaim 13 further comprising: entering a continuous angular velocity(CAV) recording mode; varying the sync clock signal as the optical headof the optical drive moves from an inner diameter to an outer diameterof said optical disk; and, tracking said sync clock signal with theencoder loop circuit.
 23. The method of claim 22 wherein a write powerof the optical head depends on a write speed of said optical drive, saidwrite power to vary linearly between a first point at the inner diameterand a destination point.
 24. The method of claim 13 further comprising:entering a partial CAV recording mode, said partial recording modecomprised of: performing a CAV recording operation under a recordingrate limit is reached, switching a motor drive of the optical drive froma CAV servo to a CLV servo; and, maintaining said encoder clock signalduring said switching.
 25. A method for positioning an optical head ofan optical disk during a recording operation, said optical disk having aplurality of tracks, the method comprising: implementing a continuousangular velocity (CAV) recording mode; varying a sync clock signal asthe optical head of the optical drive moves from an inner diameter to anouter diameter of said optical disk; and, tracking said sync clocksignal with an encoder loop circuit.
 26. The method of claim 25 furthercomprising: varying a write power of said optical head based on a writespeed of said optical drive, said write power to vary linearly between astart point and a destination point during the recording operation. 27.The method of claim 25 further comprising: entering a partial CAVrecording mode when a predetermined recording data rate limit is reach;coupling a continuous linear velocity (CLV) circuit to the optical head;and, maintaining an encoder clock signal used during the CAV recordingmode after entering the partial CAV recording mode.